Editor's Note: This paper is 1 of 9 articles in the Special IEAM Series entitled, Watershed Cumulative Effects Assessment (WCEA). The research program emanated from a 4-year Canadian Water Network initiative, “Development of The Healthy River Ecosystem Assessment System (THREATS) for Assessing and Adaptively Managing the Cumulative Effects of Man-made Developments on Canadian Freshwaters.” The objectives were to develop a framework for watershed CEA, implement portions of the framework in multiple river basins across Canada, and to develop legacy tools (i.e., THREATS decision support software) for ongoing development, use, and uptake by water stakeholders.